Honestly, the best mic I have found that works for the 2510/2600/2830's is a Workman Superstar DM-507. You can buy them on Evilbay for 12-13 bucks. I have tried MANY mics (including the infamous Astatic 575-M6) and the Superstar mic gets my vote. It's a dynamic element mic, and it has nice, full frequency response without sounding too flat or "bassy". Get the DM-507-5, which is the 5 pin, and re-wire it to the radio. You won't be disappointed.
~Cheers~